Water-soluble polymers, such as polyacrylamide and copolymers of acrylamide with other monomers, are known to exhibit superior thickening properties when said polymers are dissolved in aqueous media. Particularly well-known for this purpose are the anionic carboxamide polymers such as acrylamide/acrylic acid copolymers, including those prepared by hydrolysis of polyacrylamide. Such polymers can be used as fluid mobility control agents in enhanced oil recovery (EOR) processes.
In the past, these polymers were made available commercially as powders or finely divided solids which were subsequently dissolved in an aqueous medium at their time of use. Because such dissolution steps are sometimes time consuming and often require rather expensive mixing equipment, such polymers are sometimes provided in water-in-oil emulsions wherein the polymer is dissolved in the dispersed aqueous phase. The water-in-oil emulsions can then be inverted to form oil-in-water emulsions at their time of use. Unfortunately for many applications, existing water-in-oil emulsions do not invert as readily as desired. Furthermore, the resulting inverted emulsions are often unable to pass through porous structures. This significantly limits their utility as, for example, fluid mobility control agents in EOR applications. In addition, existing water-in-oil emulsions often cannot be efficiently inverted using an aqueous medium containing dissolved salts, as is often the case for enhanced oil recovery practices.
Accordingly, improved methods for preparing aqueous polymer solutions are needed.